The present invention relates to a fuel injection pump for internal combustion engines and in particular to a fuel injection pump including means for effecting a basic setting of the pump without affecting its structural length.
The pump under consideration includes a housing having at least one bore, and an associated cylinder bushing or flanged sleeve which is freely inserted into the housing bore for mounting the cylinder bushing to the housing. The sleeves or bushings are rotatable within a limited angular region for the basic setting of a supplied fuel quantity and are provided with a mounting flange which is clamped by bolts to the upper end face of the pump housing. In order to change the supplied fuel quantity, a pump piston is both axially and rotationally movably guided in a bore of the cylinder bushing and is provided with an oblique control edge which cooperates with at least one control bore in the wall of the cylinder bushing. In a continuation of the bore in which the piston is located, there is disposed a pressure valve which has a valve housing and a valve spring. The valve housing and/or the spring are held in their installed position within the flanged housing or the cylinder bushing by a threaded nipple. The nipple in turn serves for the outflow of the fuel which is under the influence of an injection pressure.
In known fuel injection pumps whose cylinder bushings or flanged sleeves for accepting the cylinder bushing are provided with a mounting flange, these so-called flanged elements are rotatable within a limited angular region for the purpose of setting a basic fuel quantity. Usually this is done after releasing two fastening bolts and tapping lightly with a tool on the outer edge of the mounting flange. This kind of adjustment of the flanged elements is both very time-consuming and also very highly dependent on the ability of the person doing the adjusting and, in addition, there is the danger that the flange may be damaged. Furthermore, an adjustment of this type can only be made after the fastening bolts have been released almost completely. Thus, this adjustment cannot be made when the pump is running.
In a known fuel injection system of the above described construction, the cited disadvantages are overcome at least partially by providing set screws on the flange at the level of the elongated holes which are supported by the mounting bolts screwed into the pump housing. When the flange is to be rotated for adjusting the basic fuel quantity setting, then both the mounting bolts as well as the two set screws must be released and one of the set screws must be screwed in while the other one is screwed out. After this adjustment, the set screws must be locked with lock nuts and the mounting bolts must be tightened again. This adjustment process is very time-consuming and the adjustment mechanism located on the mounting flange is very expensive and requires a considerable amount of space. The presence of the set screws increases the mutual separation of the elements in an impermissible manner when multi-cylinder injection pumps are involved and this is very disadvantageous for modern injection systems because a very compact construction is very desirable.